1. Field of the Invention
The present invention relates to an optical disk and a recording/reproducing device thereof.
2. Discussion of the Related Art
Currently, when of information is recorded on an optical disk which has a 1.6xcexc pitched spiral guide track of a recessed straight groove of about an xe2x85x9 wavelength depth(called xe2x80x9cgroove trackxe2x80x9d), a data mark 9 corresponding to the information is recorded either on the recessed groove track or on a land track positioned between two recessed groove tracks. A laser beam, which is modulated according to a coded data, is focused on a micron spot of a size of less than 1xcexc while optically detecting and tracking the center of the groove track using an actuator so as to record the information thereupon tracking the groove track by means of an actuator. DRAW(Direct Read After Write) recording media such as Asxe2x80x94Texe2x80x94Se, magnetic recording media such as Tbxe2x80x94Fexe2x80x94Co, or phase change recording media such as Gexe2x80x94Sbxe2x80x94Te are used as recording media. When reproducing the mark on the groove track thus recorded, a laser beam of a preset power is focused on a micron spot on the groove track having a size of less than 1xcexc while optically identifying and tracking the groove track. Conventionally, the push-pull tracking has been used the optically track the groove track in a recording/reproduction.
The conventional push-pull tracking will be explained with reference to FIGS. 5a, 5b, 6a and 6b. 
Referring to FIGS. 6a and 6b, in a conventional pre-groove system, data is recorded/reproduced in sector units, with 20xcx9c40 sectors in a turn of a track pitched in general 1.6xcexc. Each sector has a header region 2 and a data recording region 3 in a groove 4 of about xe2x85x9 wavelength depth. The header region 2 has wobble pits 6 and 7, and a sector mark 5, shown in FIG. 6b, consisting of a VFO(Variable Frequency Oscillator) 11 of continuous data pattern for locking a PLL(Phase Locked Loop), an AM(Address Mark) 12, a sector address identifier(ID) 13, an IEC(Identifier Error Corrector) 14 for detecting an error in the sector address identifier 13, and a postamble(PA) 15.
The wobble pits 6 and 7 on both sides of a center line 10 of the groove track 4 in the header region of FIG. 6a are provided for solving problems following from aberrations of the optical spot 8 from the center line 10 during recording or reproduction caused by an error in a push-pull tracking signal detected from a reflected/diffracted signal at the pre-groove 4 coming from a slight adjustment deviation in the optical system. In other words, the error in the push-pull tracking signal is corrected to keep the optical spot always on the track center line 10 using the unbalance of optical spot 8 intensities back from the pair of wobble pits 6 and 7 caused when an error occurs in the push-pull signal and the optical spot comes out of the center line 10 of track 4. This is a known art disclosed in JP Laid Open Patent No. S62-8341 for an composite type optical disk.
Currently, in order to record more data in an optical disk, land.groove recording is suggested in which, data is recorded on both of the land track and the recessed track to double a track density as shown in FIGS 5a and 5b. This land.groove recording is disclosed in papers such as N. Miyagawa, Y. Gotoh, K. Nishiuchi, E. Ohno and N. Akahira; xe2x80x9cLand and Groove recording for high track density on phase change optical disksxe2x80x9d, Jpn. J. Appl. Phys. 32, 5324/5328 (1993). In the push-pull tracking employed for optical tracking of the land, and groove tracks, a higher precision of tracking is required, and a slight adjustment deviation in the optical system causes a track offset which in turn causes a problem that the optical spot deviates from the center line of the land, or groove track during recording or reproduction. Consequently, even if the composite system disclosed in the JP Laid Open Patent No. S62-8341 is used, the land.groove disk still has difficulties correcting track offset errors which occur in the push-pull tracking such as incapability of disposal of the two wobble pits on both sides of the groove or land track that tend to occur when widths of the groove and land tracks become smaller to about 0.7xcexc.
Moreover, as shown in FIGS. 5a and 5b, each of the header regions 2 of the land track and the groove track should be provided with a synchronization mark and sector marks 5 such as a sector address. However, since a diameter of the optical spot is about 1xcexc, an exact reproduction of sector information is not possible when attempting to read a sector mark 5 on, for example, a groove track because there is leakage of a sector mark signal at the side of the sector mark 5 to be read if the widths of the groove and land tracks become smaller than about 0.7xcexc.
The tasks of the present invention for solve the aforementioned problems will be explained with reference to FIGS. 5a and 5b taking the composite type optical disk using so called land groove disk, in which data is recorded on both of the groove track and the land track, as an example.
FIGS. 5a and 5b illustrate header regions of the composite type having the wobble pits known from the JP Laid Open Patent No. S62-8341 employed for use in suppressing an offset of a push-pull signal in the land.groove recording which doubles a track density by recording data on both of the land track 16 and recessed groove track 17 for providing a greater recording capacity in the optical disk. Referring to FIGS. 5a and 5b, the push-pull tracking used to optically track the land track 16 or the groove track 17 requires higher precision tracking as a width of each of the land track 16 and the groove track 17 approaches about 0.7xcexc, which is about one half of the track pitch p=1.6xcexc of the conventional disk shown in FIG. 6a. Consequently an optical spot 8 comes out of a track center line 18 or 19 of the land track or the groove track. To correct the deviation, the wobble marks 6 and 7, should be added to each of the header regions 2 of the land track 16 and the groove track 17. However, if a width of each of the land and groove tracks decreases to about 0.7xcexc, it becomes difficult to reproduce wobble marks 6 and 7 having diameters of 0.35xcexc which is half of the track width of p=0.7xcexc as shown in FIGS. 5a and 5b, using a focused optical spot having a diameter D calculated to be D=1.1 by an equation D=xcex/NA, where xcex is a wavelength and NA is a numerical aperture, when xcex is set to 0.65xcexc and NA is set to 0.6. Consequently, problems in data recording/reproduction of the land.groove disk of narrow track widths are caused, such as incapability of correction of the offset occurring during the push-pull tracking, that significantly impedes putting the land.groove disk into practical use.
In addition, referring to FIGS. 5a and 5b again, besides the wobble marks 6 and 7, each of the header regions 2 of the land track 16 and the groove track 17 has, as shown in FIG. 6b, a sector mark 5 consisting of a VFO 11 of continuous data pattern for locking a PLL, an AM 12 being an address mark, a sector address identifier(ID) 13, an IEC 14 for detecting an error in the sector address identifier 13, and a postamble(PA) 15. If a width of each of the land and groove tracks becomes smaller to about 0.7xcexc, the large optical spot of 1.1xcexc diameter is likely to experience difficulties distinguishing VFO mark 11 in the header region 2 of the land track 16 from VFO mark 11 in the header region 2 of the adjacent groove track 17 due to cause cross-talk, which is a great cause of the error which occurs when reading in the signal of the header region 2, a problem in making the tracks of the land.groove disk narrower, and a significant obstacle in putting the land.groove disk into practical use.
Still further, referring to FIGS. 5a and 5b too, in the push-pull detection of the optically diffracted beams from the land track 16 and the groove track 17 employed in optical tracking the land track 16 and the groove track 17, polarities of push-pull signals of the land track 16 and the groove track 17 are opposite to each other because the land track 16 and the groove track 17 are formed opposite to each other. Consequently, it is necessary to determine whether the optical spot 8 tracks the land track 16 of the groove track and to invert a polarity of one side push-pull tracking signal. However, no method dependable exits for determining whether corresponds to a track a groove or a land, which is a significant obstacle in putting the land.groove recording into practical use.
Accordingly, the present invention is directed to an optical disk and a recording/reproducing device thereof that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the optical disk includes a land track and a groove track formed in a form of alternating spirals with widths substantially the same with the other, one turn of each of the land track and the groove track having a plurality of sectors ranging 15xcx9c45, each sector having a first region and a second data recording region, the first region having information pits such as synchronization marks and sector address marks formed in a radial direction of the optical disk and wobbled with an amplitude about a half of the width of the land track and the groove track from respective track centers on both sides thereof, and a depth of a wobbled mark being adapted to be detected by a push-pull signal.
In other aspect of the present invention, there is provided a recording/reproducing device including means for rotating the optical disk, means for directing a light beam onto the optical disk, and means for receiving the light beam reflected at a wobbling mark in a first region of each sector through a two-piece detector, determining a track of being a land track or a groove track from a push-pull signal of the received light beam, and carrying out recording/reproduction of information on/from a second data recording region.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.